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Date:   Wed, 3 May 2023 14:31:23 +0300
From:   Dan Carpenter <dan.carpenter@linaro.org>
To:     Thadeu Lima de Souza Cascardo <cascardo@canonical.com>,
        Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Cc:     Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>,
        Chuck Lever <chuck.lever@oracle.com>,
        Jeff Layton <jlayton@kernel.org>, linux-nfs@vger.kernel.org
Subject: Re: [PATCH] net: avoid double iput when sock_alloc_file fails
Message-ID: <95e36d70-7841-4e7d-960a-116b8595b820@kili.mountain>
References: <20230307173707.468744-1-cascardo@canonical.com>
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I changed the CC list from netdev to linux-nfs.

On Tue, Mar 07, 2023 at 02:37:07PM -0300, Thadeu Lima de Souza Cascardo wrote:
> When sock_alloc_file fails to allocate a file, it will call sock_release.
> __sys_socket_file should then not call sock_release again, otherwise there
> will be a double free.
> 

It's just a one liner to make Smatch warn about these sorts of user
after free bugs.

	{ "sock_release", PARAM_FREED, 0, "$" },

Smatch found a related bug in nfs.

net/sunrpc/svcsock.c:938 svc_tcp_accept() warn: 'newsock' was already freed.
net/sunrpc/svcsock.c:1633 svc_create_socket() warn: 'sock' was already freed.
net/sunrpc/svcsock.c:1555 svc_addsock() error: dereferencing freed memory 'so'
net/sunrpc/svcsock.c:1633 svc_create_socket() warn: passing freed memory 'sock'
net/sunrpc/svcsock.c:938 svc_tcp_accept() warn: passing freed memory 'newsock'

I guess the svc_setup_socket() function should free sock on every error
path?  It seems kind of gnarly.

I fixed another sock_release() double free in xen that was simpler.

regards,
dan carpenter